Who is Alexandre St.-Germain from The Midnight Club and what is their importance?

Isiah Parker is a policeman who works in the same Harlem neighborhood where he has lived all his life. Isiah likes to be a cop and likes the idea of making his old neighborhood safer for his friends and neighbors. Isiah had a brother who was a promising boxer. This brother, Marcus, got involved with organized crime in order to further his boxing career. However, something went wrong and Marcus was found dead of a drug overdose in a dilapidated hotel in a poor section of the city. Isiah believes that St.-Germain killed his brother because he would not throw a fight. Isiah is filled with anger and grief and wants to get St.-Germain back for what he has done.